Ducts fabricated from fiber glass boards have long been used in the transportation of heated or cooled air. Typically, treated air is supplied to a duct through an intake vent and is moved through the duct to various outlets by means of a fan. This produces either a positive or negative pressure condition inside the duct which, if sufficiently high, tends to bow the duct walls and eventually weaken the joints between the walls. It is often necessary to reinforce the ducts against these forces.
Ducts are commonly reinforced by threading a wire through opposite walls of the duct and securing the ends of the wire to prevent them from slipping through the wall into the interior of the duct. This provides the needed tensile strength to hold the duct walls in place, but at the same time increases the cost of the duct due to the added time of fabrication. This added time can be three to four times as much as other fabrication steps. This is because the layout of the reinforcing wire and the actual threading and installation of the wire have been done by hand.
It would be desirable to be able to automatically install reinforcing wire so that this phase of the fabrication process could be done as efficiently as the semi-automatic cutting and grooving operation. Until now, there has not been a satisfactory machine for accomplishing this.